DES MOINES — Retired Des Moines businessman Fred Hubbell appeared to be on his way to landing the Iowa Democratic Party’s 2018 gubernatorial nomination in Tuesday’s five-way primary race and the opportunity to challenge Republican Gov. Kim Reynolds in the November general election.Hubbell, 67, was the top vote-getter early with nearly 57 percent of the ballots — a margin of victory that exceeded the 35 percent threshold required by Iowa law to win the nomination outright rather than have the decision go to Democratic delegates at this month’s state convention.